Golf MK4 1.4 16V Mis fire rough running

8 Nov 2006
Reaction score
United Kingdom
HI All

I have a Golf MK4 1.4 16v which had the engine light come on.

AA diagnosed codes P0300 and P0304

I changed the spark plugs in January of this year and replaced the HT Leads as well a few months back.
Codes came back and I also changed the Coil Pack and also renews the fuel filter. Now again the same codes have come up!! At a loss as to what to check / replace next! Anyone have any ideas or even come across this persistent problem before or have cured it? Many thanks
Sponsored Links
P0304 is a misfire on cylinder 4 and P0300 is just logging a random misfire.
Worth checking the coil packs again, did you fit oe spec parts?
Hi CH427

I obtained one form a UNipart store once they had my Reg Number so being not part savvy think its is OE ??
Had a Beetle with the same problem, never got the chance to cure it, the owner sold it on.
Check No 4 spark plug for different colour than the other 3. Look for oiling/black, it should be a sort of brown in colour.
Also check the loom going to No4 injector in the inlet manifold. Might be worth switching the injector with No3?
Just keep an open mind, we had a Lupo that threw that code and it was the Lambda sensor (the back one behind the Cat box). Might be worth disconnecting the plugs to both, to see are the terminals clean.

A compression test when the engine is hot and then when cold. You will be looking for a low reading on No4 compared to the other cylinders. But do the easy/cheap stuff first.
Sponsored Links
Hi Mursal

Plus look fine no Oil or sooty deposits just grey / brown on colour, they are NGK replaced last January.

I had a Scan done on the car Ross Tech?

No faults found in the engine module apart from the 2 Codes mentioned so does that mean Lambda sensors are OK?

Bugs the hell out of me as the Car is smooth on start up but jerks at slight accelaration until warm. When the car stops on an upward incline the engine really judders and jerks but no drop in RPM which is steady. When stood still on a decline the engine is smooth as should be, really weird!!
are we talking individual coil packs on these?
If so try switching the coil packs around on say cylinders 3 and 4 and see if the misfire code moves (clear all codes before you re start the engine)
Hi ch427

The Coil Pack is just one unit, just wondering if the coil pack is faulty not sure if that shop will honour a refund or replacement as they may fault maybe with another component?

Will swapping the injector leads not harm the engine?
Its unusual for a cylinder to go down when using 1 coil pack but not unheard of. I meant to swap the coil packs on cylinders not the injectors but this is not possible with a single pack.
Is this a single point type injection?
Hi ch427

Don't know if it is a single point injection system but does have a fuel rail and 4 injectors and is a 1.4 16V golf Mk4.

I took it back to the Chap who did the Ross Tech who cleared the codes and then checked for individual cylinder misfire. Cylinder 4 was the one which continually registered a Mis Fire!!

Odd the car misfire or idles very roughly when on an incline but is smooth on a downward part of a hill!
Its a multi point injection system.....single point injection cars have one large fuel injector where the carburettor used to be.
You need to check the resistance across number 4 fuel injector, and about 16 ohms should be correct.
Then its a compression test on that pot....looking for 200 psi or over.
John :)
Hi Burnerman

Thanks for the reply and apologies in getting back to you. Checked Injector resistance and is at 16 Ohms. Unfortunately I do not have a compression tester although now what happens is that the codes appeared again when engine mangement light came on but light disappeared a day or so later. Now what happens is that the engine management light flashes when I am coasting down hill in neutral! If I then put the car in gear and accelerate the Engine managment light stops flashing!!
I think you may be confusing the ECU by coasting downhill in neutral, (the engine is rotating slower than it thinks it should) and random management lamp issues are often caused by exhaust issues.
Whats the state of play now?
John :)
Hi Burnerman

Took the car for another opinion and old fashioned mechanic thought that cyclinder 3 had a stuck compkression ring hence misfire. Oil Flushed and thicker Halfords 20 / 50 Oil added to loosen and add lubrication to stuck ring.

Codes I still get are 16684 -

Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16688 - Cylinder 4: Misfire Detected
P0304 - 35-00 -
and now

01039 - coolant temperature sensor (g2) 30-10 - open or short to plus - intermitten

Will renew Temp Sensor but now really abffled why engine judders os badly sometimes!!
I think we may be getting a bit carried away here.....a stuck compression ring being freed off by adding a 20/50 lubricant? I wonder where he gets that one from.....
A compression test is essential, and the only real way to tell if a cylinder is well or not.
I would imagine this engine has hydraulic valve lifters - I'd be using a thin oil if I suspected any issues here.
Coolant temperature sensors are notorious items for failing in this age of VW, but its usually a poor tickover that shows that one - well worth replacing though.
John :)
Sponsored Links